Elastomers, based on the condensation of a major proportion of thiodiethanol with one or more aliphatic diols containing a sulfur-vulcanizable double bond, are described by Aloia, U.S. Pat. No. 3,951,927; Chang et al., U.S. Pat. No. 3,985,708; Chang, U.S. Pat. No. 4,000,213; and Li et al., U.S. Pat. No. 4,028,305, all of which are incorporated herein by reference. Heretofore, application of conventional sulfur vulcanization systems, e.g., sulfur, zinc oxide, benzothiazole sulfenamides, thiuram sulfides, mercaptobenzothiazole, and the like, to the vulcanization of these elastomers has been less than satisfactory. Zinc oxide has heretofore been considered to be essential to the vulcanization of unsaturated elastomers with sulfur. In the vulcanization of thiodiethanol-based elastomers of the invention, conventional sulfur-vulcanization systems containing zinc oxide result in a fast cure, but the vulcanized elastomers exhibit poor heat ageing as manifested by high compression set and poor continuous stress-relaxation. However, when zinc oxide is omitted from the cure system, the cure rate is impractically slow. All of these factors indicate that there is a need for a vulcanization system to vulcanize thiodiethanol-based elastomers.
In order for an elastomer to achieve commercial success, it must be vulcanizable to useful products with an efficient, practical vulcanization system. It is an object of the invention to provide such a system. It is also an object of the invention to provide useful vulcanized products from thiodiethanol-based elastomers, and to provide elastomers exhibiting significantly improved aged properties, such as compression set.